Response to repeated equal doses of epinephrine during cardiopulmonary resuscitation in dogs

Study objective: Advanced cardiac life support (ACLS) guidelines recommend a 3- to 5-minute interval between repeated doses of epinephrine. This recom mendation does not take into account the dose of epinephrine used, and only very limited data exist regarding the hemodynamic responses to repeated "h igh" doses of epinephrine. The objective of this study was to analyze the h emodynamic responses to repeated, equal, high doses of epinephrine administ ered during cardiopulmonary resuscitation (CPR) in a canine model of ventri cular fibrillation (VF). Methods: This study used a secondary analysis of data collected in a prospe ctive, randomized study, primarily designed to assess the effects of acid b uffers in a canine model of cardiac arrest. VF was electrically induced. Af ter 10 minutes, CPR was initiated, including ventilation with FIO2=1.0, ext ernal chest compressions, administration of epinephrine (0.1 mg/kg repeated every 5 minutes) and defibrillation. Animals were randomized to receive ei ther NaHCO3, Carbicarb, tromethamine (THAM), or NaCl. The hemodynamic varia bles were sampled from each experiment's paper chart at 1-minute intervals, and the responses to the first 4 doses of epinephrine were compared. Results: Thirty-six animals (9 in each buffer group) were included in this analysis. Systolic, diastolic, and coronary perfusion pressures increased s teeply (by 100%, 130%, and 190%, respectively) only after the first epineph rine dose. These pressures peaked at 2 to 3 minutes and decreased only slig htly and insignificantly during the rest of the 5-minute interval, until th e next epinephrine dose. No further significant increases in arterial press ures were observed in response to the next 3 doses of epinephrine, administ ered 5 minutes apart. Conclusion: The hemodynamic effects of high-dose epinephrine (0.1 mg/kg) du ring CPR appear to last longer than 5 minutes. Therefore, longer intervals between doses may be justified with high doses of epinephrine.